A 36- year - old factory worker developed itchy, annular scaly plaques in both groins. Application of a coicosteroid ointment led to temporary relief but the plaques continued to extend at the periphery. The most likely diagnosis is -

<p>DERMATOPHYTOSIS Infection caused by dermatophytes.Superficial cutaneous infection.Affects stratum corneum layer of skin.Dermatophytes belonging to genera microsporum,Trichophyton and epidermophyton causes ringworm/tinea of skin ,hair and nails. Classified based on site of involvement.1. T.corporis- Glabrous skin.(skin regional except scalp,groin,palms and soles.2. T.cruris- groin.3. T.faciei- face4. T.barbae-Beard5. T.pedis-soles and web spaces.6. T.manuum-palms and webspaces.7. T.unguium-finger and toe nail. Tinea cruris:- Affect skinfolds especially groin. Also known as dhobie itch. Lesions -itchy erythematous scaly plaques with a burning sensation. Following central resolution,lesion become annular in shape. Some crusting seen peripherally with central clearing. itchy annular lesions with central clearing and extending border is diagnostic of tinea. lesions of granuloma annulare will show beaded appearance at the margin without scaling. Most common in diabetics erythema annulare centrifugum appear as annular erythema without scaling and central clearing. Annular lichen plants lesions present as flat annular plaques with hypo pigmented border most common over the sun exposed sites. Iadvl textbook of dermatology page 263